Computed tomography (CT) was performed in 43 cases of colonic diverticulitis and compared with the contrast-enema examination (CE) in 37 patients. Findings on CT included inflammation of the pericolic fat in 98% of cases, diverticula in 84%, thickening of the colon wall in 70%, a pericolic abscess in 35%, peritonitis in 16%, a fistula in 14%, colon obstruction in 12%, and intramural sinus tracts in 9%. Secondary findings included a distant abscess in 12% and ureteral obstruction in 7%. In addition to detecting ureteral and bladder involvement and distant abscess formation, CT was preferable for demonstrating the extent of pericolic inflammation, which was underestimated with CE in 41% of patients. Differential diagnosis of the CT findings is discussed. The authors indicate that CT should be the initial procedure in patients with suspected diverticulitis, particularly when CE is contraindicated.